Abrasive article



E.v B. WYATT ABRASIVE ARTICLE May 10, 1932.

Filed Jan. 5. 1929 Vgl- Patented May (l0, 1932 UNITED STATES PATENT OFFICE nENEsT E. wYATT,` or' IIADEONEIELD, NEW JERSEY, AssIGNoE, BY MEsNE AssIeN- MENTs, To MINNESOTA MINING AND MANUEAcTUEINe COMPANY, or sT. TAUL, MINNESOTA, A coEroBATIoN E DELAWARE AEEAsIvE ARTICLE Applica/mn med January 5, 192s. serial No. 330,666.

an adhesive binder, the exposed outer surface of the abrasive material so bonded forming the cuttin face for the abrasive article.

One di culty with abrasive articles of the kind just mentioned ils that the exposed portion or cutting face presented by the abrasive material does not possess sufficient roughness to have the highest degree of eciency.

The object of the invention is to overcome the diliculty just referred to by improving, in the sense of making more effective as a cutting agent, the cuttingl face of the abrasive e abrasive material..A

article as presented by t It will first be explained that the abrasive grain or particle now commonly employed in the making of abrasive articles, is a grain possessin irregularity in formwith sharp cutting e ges or points. Owing to the irregu-v larity in the form of the abrasive grain or particle a certain sectional portion of the grain will be larger in size and accordingly heavier than the remaining portion thereof and it is that section of the grain having the lesser body which presents the better cutting edge or point. This peculiarity of the ain itself is referred to at this time because '1t-is availed of, at least in part, in theppresent invention. n

The improved abrasive article constituting my invention consists in one in which the abrasive material is bonded by a suitable.

binder to a base'sheet or backing, usually of cloth or paper, and in which the abrasive grains forming the abrasive materiaL'lie or are so ositioned that those portions or sec- 40 tions oi) the grains possessing the larger body will lienearest the base sheet or backing, while those ortions or sections of the grains lpossessing the lesser body and the better cutting edge or' points, are directed away from 5 the base sheet or backing. The disposition ,Y pass throu of the grains is also such that they will occupy positions unimpacted with relation to one another, nnpacting of the grains causing the cutting surface' .presented by them` to be smoothed out or leveled which impairs its .50 cutting eliciency as when the abrasive grains, Vhaving been applied to a base sheet or backing with unset binder thereon, are passed through or beneath press rolls.

The improvement can better be understood 1n the lig t of the way in which the abrasive article is made and in the light also of the Figure 1- is a cross section of the improved abrasive article.

Fig. 2 shows diagrammatically in cross section certain apparatus used in` making the article, and

Fig. 3 is 'a plan of a portion of the apparatus.

Referring to the drawings 1 is the base sheet or backing, 2 the abrasive material consisting of `abrasive grains or particles, and -3 the binder by which the abrasive grains are bonded to the base sheet. 70'

In the making of the article the base sheet or backi'n ,to which the binder material has been app ied, is passed throu h or over a troughlike receptacle 4, idler ro s 5 assisting in the support of the sheet and the sheet being .propelled by any suitable mechanism (not shown) Located above the sheet isa hopper 6 containing the abrasive grains or particles to be applied to the sheet. The hopper Vis provided at the bottom with a mouth 7 nor- 30 mally closed by a roll 8 excepting for an opening 9 left at the bottom of the hopper adjacent the top side of the'roll and through which opening the abrasive material will escape to h the opening out over the roll 8 35 as the rol is turned. The material thus escapingto pass over the roll 8 is directed by a guard 1l) to fall by 'gravity onto a roll 11l arranged beneath the roll 8, and from the roll 11 the abrasive material is directed to fall 90 b avit onto the sheet or backing passing bgngeth the hopper and the respective rolls. The roll 11 may have co-operating with it a roll 12 for assisting in the directing of the abrasive material onto the sheet, but this second roll is not necessary. All the rolls` may be rotated by any suitable mechanism (not shown). In practice onlyA so much of the abrasive material is applied to the sheet or backing as will remain upon it and become bonded to it. Accordingly, taking into con` sideration the rate o'fspeed at which the sheet is moving beneath the hopper, only a determinate amount of the abrasive material is allowed to escape through the opening 9 left at thebottom of the hopper, for which reason the openinor 9 is provided with a gate 13 located on the hopper.

Arranged beneath the sheet in position to engage the under side thereof are rotary beaters 15. One of these beaters is preferably placed directly beneath the point where the abrasive material is being deposited upon the sheet and the other one Yof the lbeaters is located a little forward ofthe iirst beater. The beaters are rotated by any suitable mechanism (not shown) at a very high rate of speed during the time when the abrasive material is being deposited upon the sheet whereupon the following effectvwill be obtained: The violent vibration -of the sheet by the beaters has but little effect on the posit-ioning of the abrasive grains immediately next to the backing sheet for these grains will be wetted by the cementing material and will adhere to it. Other of the abrasive grains will be batted into the air and drop back or settle by gravity on the sheet in a manner fairly describable as free fall, in which the shape and weight of the particle will determine the position it takes on the backing. In other words, the larger or heavier portions or sections of the grains will face the sheet `or backing, while the smaller portions, or sections, or those which present the better y cutting portions or edges, will be directed away om the sheet or backing. The grains or particles thusffalling'will become bonded to the sheet or bac-king as the cementing material will have wetted the lirst layer. of particles whereupon more particles will be held to the sheet as they fall byv gravity onto it in the natural travel ofthe backing. In', his way a coating is achieved whichv may bldescribed as an oriented coating or one in which 'the grains are placed in positions most effective for cutting operations. The application of the grains or particles, falling gently asthey do by gravity after being thrown into the air, leavesthem relatively isolated and unimpacted with relation to one another. That is, the deposited abrasive material is left as it falls and is not subjected to any rolling action or pressure which will cause impaction thereof or levelling. and consequent of the coating so that the grains or particles thrown into the air and falling back onto the sheet willbecome wetted and adhere to the sheet there is preferably arranged over the sheet above the point where the beaters are in engagement therewith 'a fixed grid 16 which operates to keep vair currents away from the cementing material and also from the falling grains themselves in order that both the bonding material and the grains will be; as little influenced by disturbing air currents as possible. The grid also assists in directing the abrasive grains thrown into the air in a direction where they will fall bclr onto the sheet instead of falling off the s eet.

In Isome operations the application of the abrasive ains or mineral to the coated backing may e so lean and scant that only one layer of the abrasive will be applied to the backing. In such case there will be practically no batting of the mineral into the air as described above for the reasonthat substantially all of the ap lied abrasive will adhere to the backing. n such case, however,

the applied mineral will be given a firmer In practice the surface of the deposited abrasive material is subjected to a binder coating 17 which co-operating with the binder applied to the Vsheet or backing, assists in holding in place the abrasive grains or particles which form the outer portion or true cutting face of the deposited material.

vI-Iaving thus fully described my invention, I claim and desire to secure by Letters Patent of the United States 1. The method of making an abrasive artiele having a backing, a facing of abrasive material and a binder bonding the abrasive material to the backing, which comprises ap' plying the abrasive material in determinate quantity to the running backing coated with binder material and at the place of application'and during the time of such application rapidly vibrating the backing by an application of force to the rear side thereof whereby a portion of the vdeposited material will be thrown into the air above the backing and afterward settle back onto the backing.

2. The method of making an abrasive article having a backing, a 'facing of abrasive material and a binder bonding the abrasive material to the backing, which comprises minata quantity -to the running backing coated with binder material and at the place of applying the abrasive material in deter@4 A application and during the time lof such application rapidl vibrating the backing by an application of orce to the rear side there of whereby a portion of the deposited ma.- terial will be thrown into the air above the backing 'and afterward settle back onto the backing, the area immediately adjacent and above the backing into which the abrasive materiel is projected being kept free from disturbing air currents.

ERNEST B. WYATT. 

